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Dedicated Instances

Dedicated Instances are Amazon EC2 instances that run in a virtual private cloud (VPC)
on hardware that's
dedicated to a single customer. Dedicated Instances that belong to different AWS
accounts are physically
isolated at the hardware level. In addition, Dedicated Instances that belong to
AWS accounts that are
linked to a single payer account are also physically isolated at the hardware level.
However, Dedicated Instances may share hardware with other instances from the same
AWS account that are
not Dedicated Instances.

Note

A Dedicated Host is also a physical server that's dedicated for your use.
With a Dedicated Host, you have visibility and control over how instances are placed
on the
server. For more information, see Dedicated Hosts.

Dedicated Instance Basics

Each instance that you launch into a VPC has a tenancy attribute. This attribute has
the following values.

Tenancy Value

Description

default

Your instance runs on shared hardware.

dedicated

Your instance runs on single-tenant hardware.

host

Your instance runs on a Dedicated Host, which is an isolated server with
configurations that you can control.

After you launch an instance, there are some limitations to changing its
tenancy.

You cannot change the tenancy of an instance from default to
dedicated or host after you've launched it.

You cannot change the tenancy of an instance from dedicated or
host to default after you've launched it.

You can change the tenancy of an instance from dedicated to
host, or from host to dedicated after you've
launched it. For more information, see Changing the Tenancy of an Instance.

Each VPC has a related instance tenancy attribute. This attribute has the following
values.

Tenancy Value

Description

default

An instance launched into the VPC runs on shared hardware by
default, unless you explicitly specify a different tenancy during instance
launch.

dedicated

An instance launched into the VPC is a Dedicated Instance by
default, unless you explicitly specify a tenancy of
host during instance launch. You cannot specify a
tenancy of default during instance launch.

You can change the instance tenancy of a VPC from dedicated to
default after you create it. You cannot change the instance tenancy of
a VPC to dedicated.

To create Dedicated Instances, you can do the following:

Create the VPC with the instance tenancy set to dedicated (all
instances launched into this VPC are Dedicated Instances).

Create the VPC with the instance tenancy set to default, and
specify a tenancy of dedicated for any instances when you launch
them.

Dedicated Instances Limitations

Some AWS services or their features won't work with a VPC with the instance tenancy
set
to dedicated. Check the service's documentation to confirm if there are any
limitations.

Some instance types cannot be launched into a VPC with the instance tenancy set to
dedicated. For more information about supported instances types, see Amazon EC2 Dedicated Instances.

Amazon EBS with Dedicated Instances

When you launch an Amazon EBS-backed Dedicated Instance, the EBS volume doesn't
run on single-tenant hardware.

Reserved Instances with Dedicated Tenancy

To guarantee that sufficient capacity is available to launch Dedicated Instances,
you can purchase Dedicated Reserved Instances. For more information, see Reserved Instances.

When you purchase a Dedicated Reserved Instance, you are purchasing the capacity
to launch a Dedicated Instance into a VPC at a much reduced usage fee; the price
break in the usage charge applies only if you launch an instance with dedicated
tenancy. When you purchase a Reserved Instance with default tenancy, it applies only
to a
running instance with default tenancy; it would not apply to a
running instance with dedicated tenancy.

You can't use the modification process to change the tenancy of a Reserved Instance
after
you've purchased it. However, you can exchange a Convertible Reserved Instance for
a new Convertible Reserved Instance with a
different tenancy.

Automatic Scaling of Dedicated Instances

Automatic Recovery of Dedicated Instances

You can configure automatic recovery for a Dedicated Instances if it becomes impaired
due to an
underlying hardware failure or a problem that requires AWS involvement to repair.
For more information, see Recover Your Instance.

Pricing for Dedicated Instances

Working with Dedicated Instances

You can create a VPC with an instance tenancy of dedicated to ensure
that all instances launched into the VPC are Dedicated Instances. Alternatively, you
can
specify the tenancy of the instance during launch.

Changing the Tenancy of an Instance

Depending on your instance type and platform, you can change the tenancy of a
stopped Dedicated Instance to host after launching it. The next time
the instance starts, it's started on a Dedicated Host that's allocated to your
account. For more information about allocating and working with Dedicated Hosts, and
the instance types that can be used with Dedicated Hosts, see Working with Dedicated Hosts.
Similarly, you can change the tenancy of a stopped Dedicated Host instance to
dedicated after launching it. The next time the instance starts,
it's started on single-tenant hardware that we control.

Changing the Tenancy of a VPC

You can change the instance tenancy attribute of a VPC from
dedicated to default. Modifying the instance tenancy
of the VPC does not affect the tenancy of any existing instances in the VPC. The
next time you launch an instance in the VPC, it has a tenancy of
default, unless you specify otherwise during launch.

You cannot change the instance tenancy attribute of a VPC to
dedicated.

You can modify the instance tenancy attribute of a VPC using the AWS CLI, an AWS SDK,
or the Amazon EC2 API only.

To modify the instance tenancy attribute of a VPC using the AWS CLI

Use the modify-vpc-tenancy
command to specify the ID of the VPC and instance tenancy value. The only
supported value is default.